refactor: improve code quality and efficiency in various files (#548)

- Replace loadConfig() with _ = loadConfig()
- Update file permissions from 0660 to 0o660
- Simplify variable declarations
- Replace golang.org/x/crypto/ssh/terminal with golang.org/x/term
- Remove unused getCertPrincipals function
- Replace time.Now().Sub() with time.Since()
- Add test for ArgToIndex function

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-on: https://gitea.com/gitea/tea/pulls/548
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: techknowlogick <techknowlogick@noreply.gitea.io>
Co-authored-by: appleboy <appleboy.tw@gmail.com>
Co-committed-by: appleboy <appleboy.tw@gmail.com>

modules/interact/comments.go

@@ -13,7 +13,7 @@ import (
 	"code.gitea.io/tea/modules/print"
 
 	"github.com/AlecAivazis/survey/v2"
-	"golang.org/x/crypto/ssh/terminal"
+	"golang.org/x/term"
 )
 
 // ShowCommentsMaybeInteractive fetches & prints comments, depending on the --comments flag.
@@ -72,5 +72,5 @@ func ShowCommentsPaginated(ctx *context.TeaContext, idx int64, totalComments int
 
 // IsStdinPiped checks if stdin is piped
 func IsStdinPiped() bool {
-	return !terminal.IsTerminal(int(os.Stdin.Fd()))
+	return !term.IsTerminal(int(os.Stdin.Fd()))
 }